The invention relates to a method and a corresponding parking assistance system for performing an automated parking process for a motor vehicle in a parallel parking space arranged parallel to the direction of the road, wherein the vehicle controls the longitudinal and tranverse movement of the vehicle automatically.
In parking assistance systems with automated tranverse guidance, i.e. with automatic control of the transverse movement of the vehicle, the steering of the vehicle during the parking process into a parallel parking space is undertaken by the parking assistance system. The longitudinal guidance must be undertaken by the driver himself by means of appropriate acceleration and braking. In parking assistance systems with automated transverse and longitudinal guidance, this task of longitudinal guidance is also undertaken by the parking assistance system; the vehicle controls the longitudinal and transverse movement of the vehicle automatically. In such parking assistance systems with automated transverse and longitudinal guidance, the driver generally has the option of being able to have the vehicle parked and optionally taken out of the parking space automatically at the touch of a button.
An exemplary parking assistance system with automated tranverse and longitudinal guidance is described in the document “Parking assistant with longitudinal and transverse guidance”, Dirk Ahrens, 5th Driver Assistance Conference of TU München, Münich, 2012.
A further parking assistance system with automated transverse and longitudinal guidance is described in the document WO 2006/050710.
In established parking assistance systems with automated transverse and longitudinal guidance, the vehicle is moved in one or more moves into a final parking position in the parallel parking space in which the vehicle is oriented substantially parallel to a lateral boundary line of the parallel parking space in the longitudinal direction and is at an admissible distance from the lateral boundary line of the parallel parking space. The lateral boundary line is formed by the curb, for example.
A disadvantage of this is that the parking process is completed independently of the longitudinal orientation of the vehicle in the parallel parking space; only the distance from the lateral boundary line (i.e. typically the distance from the curb) and the vehicle skew (i.e. whether the vehicle is oriented parallel to the lateral boundary line) are rated.
Since the longitudinal orientation of the vehicle in the parking space is not taken into account when the parking process is completed, an unnecessarily large amount of parking space is wasted. If, when the vehicle is parked in a large parking space, for example, the vehicle comes to a standstill in the middle of the parking space as the final parking position, parking space in front of and behind the vehicle is wasted unnecessarily.
Furthermore, it may be difficult for the driver to take the vehicle out of the parking space manually later if, in the final parking position, the distance between the front of the vehicle and the rear of the bounding vehicle parked in front is short.
It is an object of the invention to provide a method for performing an automated parking process with automated transverse and longitudinal guidance that is improved in respect of these disadvantages, as well as to provide a corresponding parking assistance system.
This and other objects are achieved in a first aspect of the invention by a method for performing an automated parking process for a motor vehicle in a parallel parking space, wherein the vehicle controls the longitudinal and transverse movement of the vehicle automatically, which involves the vehicle being moved in one or more moves into an oriented position in the parallel parking space in which the vehicle is oriented substantially parallel to a lateral boundary line of the parallel parking space in the longitudinal direction and is at an admissible distance from the lateral boundary line of the parallel parking space. This oriented position corresponds to the final parking position in conventional parking assistance systems with automated transverse and longitudinal guidance.
The method according to the first aspect of the invention is distinguished in that the distance from a bounding object at the front (frequently: bounding vehicle at the front) of the parking space is determined in the oriented position (in which the vehicle is preferably at a standstill) and then, on the basis of the distance, the vehicle performs an additional corrective move in which the vehicle moves in the forward direction or the reverse direction under automatic control with a steering angle of substantially zero degrees. A steering angle of substantially zero degrees means that the vehicle moves in the forward direction or the reverse direction in the longitudinal direction of the vehicle.
The proposed additional corrective move allows the attainment of an optimum longitudinal orientation in the parking space. This allows the parking space requirement to be kept small and, furthermore, it is possible to attain a distance from the bounding vehicle at the front that facilitates taking the vehicle out of the parking space later since the parking process is not completed too close to the bounding object at the front.
Advantageously, in an additional corrective move with a steering angle of zero degrees, the distance of the vehicle is corrected to a prescribed target distance from the bounding object at the front (frequently bounding vehicle at the front). By way of example, the prescribed target distance corresponds to a value in the range from 50 cm to 110 cm, particularly in the range from 70 cm to 90 cm, for example 80 cm. When the distance from the bounding object at the front is corrected to a prescribed target distance in the range from 70 cm to 90 cm, the available parking space is utilized well and at the same time an adequate distance from the bounding object at the front is left, so that it is a simple matter to take the vehicle out of the parking space later in one move (i.e. without reversing the vehicle).
The distance can be corrected depending on the distance from the bounding object at the front either by maneuvering forward or by maneuvering backward with a steering angle of zero degrees. In the first case, the vehicle moves up to a prescribed target distance from the bounding object at the front.
In the oriented position, according to an advantageous embodiment, a check is performed to determine whether the distance from the bounding object at the front is greater than (or, in an alternative embodiment: greater than or equal to) a first threshold value (for example 1.1 m); in this case (subsequently called case 1), the vehicle is too far away from the bounding object at the front. In this case 1, the vehicle automatically heads toward the bounding object at the front in the forward direction with automated transverse and longitudinal guidance as part of the corrective move and, in so doing, reduces the distance from the bounding object at the front.
If, by contrast, the distance from the bounding object at the front is less than or, in an alternative embodiment, less than or equal to a prescribed third threshold value (for example 0.5 m) and the vehicle is therefore too close to the bounding object at the front, then in this case (subsequently called case 2) the vehicle automatically heads away from the bounding object at the front in the reverse direction with automated transverse and longitudinal guidance as part of the corrective move.
In this case, the third threshold value (for example 0.5 m) is preferably less than the first threshold value (for example 1.1 m), which means that an intermediate range is obtained between the first and third threshold values. Alternatively, it would be conceivable for the third threshold value to correspond to the first threshold value.
Preferably, if case 1 is present and the distance from the bounding object at the front is greater than or greater than or equal to the first threshold value in the oriented position, then the vehicle is headed in the forward direction toward the bounding object at the front as part of the corrective move until the distance from the bounding object at the front reaches a second threshold value (e.g. 0.9 m), provided that at this moment the distance from the bounding object at the rear meets a particular condition at the same time. In this case, the second threshold value (e.g. 0.9 m) is less than the first threshold value (e.g. 1.1 m), since the vehicle is moving in the forward direction toward the bounding object at the front. When this second threshold value is reached and the condition in relation to the distance from the bounding object at the rear is met, the heading toward the bounding object at the front is completed; in that case, by way of example, the drive torque is reduced to zero or to a negative value and a braking torque is set by way of the service brake in order to stop the vehicle; preferably the vehicle does not come to a standstill immediately, however, but rather, owing to the inertia of the vehicle, will still move a certain distance Δs in the forward direction, for example approximately 10 cm, after the second threshold value is reached. In this case, a final distance (e.g. 0.8 m) from the bounding vehicle at the front would be obtained that corresponds to the second threshold value reduced by Δs. Alternatively, it would also be conceivable for the vehicle to head toward the second threshold value for the distance from the bounding vehicle at the front at a speed steadily decreasing to zero, so that the vehicle comes to a standstill at the same time as the second threshold value is reached.
As a condition in relation to the distance from the bounding object at the rear, it is possible to check, by way of example, whether (when the second threshold value is reached by the distance from the bounding object at the front) the current distance from the bounding object at the rear is substantially greater than or greater than or equal to the current distance from the bounding object at the front. In this case, it is possible to take account of an optional tolerance, so that a check is then performed to determine whether the distance from the bounding object at the rear plus the tolerance (for example a tolerance of 0.1 m) is greater than or greater than or equal to the current distance from the bounding object at the front. In this case, when the second threshold value is reached, the vehicle will then complete the heading toward the bounding object at the front; otherwise, the vehicle will continue to head toward the bounding object at the front. After the distance from the bounding object at the front has dropped below the second threshold value, the vehicle will continue to head toward the bounding object at the front in the forward direction, until the distance from the bounding object at the front substantially (i.e. for example optionally taking into account a tolerance of 10 cm, for example) corresponds to the distance from the bounding object at the rear; the heading toward the bounding object at the front is then completed. In this case, the vehicle is thus oriented substantially centrally in the parallel parking space in the longitudinal direction.
Preferably, if case 2 applies and the distance from the bounding object at the front is less than or less than or equal to the third threshold value in the oriented position, then the vehicle will head away from the bounding object at the front in the reverse direction as part of the corrective move until the distance from the bounding object at the front reaches a fourth threshold value (e.g. 0.7 m). In this case, the fourth threshold value (e.g. 0.7 m) is greater than the third threshold value (e.g. 0.5 m), since the vehicle is moving away from the bounding object at the front in the reverse direction. When this fourth threshold value is reached, the heading away from the bounding object at the front is completed; however, the vehicle preferably does not come to a standstill immediately, but rather, owing to the inertia of the vehicle, will still move a certain distance Δs in the reverse direction, for example approximately 10 cm, after the fourth threshold value is reached.
The fourth threshold value is preferably less than the second threshold value by 2·Δs. In this case, in case 1, when heading toward the bounding object at the front is completed when the second threshold value (e.g. 0.9 m) is reached, and in case 2, when heading away from the bounding object at the front is completed when the fourth threshold value (e.g. 0.7 m) is reached, the vehicle comes to a standstill approximately at the same final distance (e.g. 0.8 m when Δs=10 cm) from the bounding object at the front.
For small parking spaces, heading away from the bounding vehicle at the front in the reverse direction does not have to be completed only when the fourth threshold value is reached, however; instead, in small parking spaces, the vehicle can complete the heading away from the bounding object at the front earlier, namely when the distance from the bounding object at the rear becomes substantially (i.e. optionally taking into account a tolerance) less than the distance from the bounding object at the front, for example. In this case, the vehicle is thus oriented substantially centrally in the parallel parking space in the longitudinal direction.
Preferably, the third threshold value (for example 0.5 m) for the heading away from the bounding object at the front in the reverse direction is less than the first threshold value (for example 1.1 m) for the heading toward the bounding object at the front in the forward direction, which means that an intermediate range is obtained between the first and the second threshold values.
Preferably, if the distance from the bounding object at the front is less than or equal to or less than the prescribed first threshold value (e.g. 1.1 m) (i.e. case 1 is not present), and additionally the distance from the bounding object at the front is greater than or equal to or greater than or equal to the third threshold value (0.5 m) (i.e. case 2 is not present), then fundamentally no corrective move is performed, in order to avoid a brief start in the forward direction or the reverse direction.
Optionally, the nonperformance of a corrective move as an additional cumulative condition may alternatively be dependent on the distance from the bounding object at the rear in the oriented position. By way of example, in the oriented position, it is possible to perform a check to determine whether the distance from the bounding object at the rear is greater than or greater than or equal to a fifth threshold value (e.g. 0.4 m; the fifth threshold value is preferably less than the third threshold value) and performance of the corrective move can be prevented if case 1 and case 2 are not present and this cumulative condition (this case is subsequently referred to as case 4) is present. If, by contrast, the vehicle is close to the bounding object at the rear and hence the distance from the bounding object at the rear is less than or equal to or less than the fifth threshold value and case 1 and case 2 are not present (this case is subsequently referred to as case 3), the vehicle is headed away from the bounding object at the rear in the forward direction as part of the corrective move, until the distance from the bounding object at the rear substantially corresponds to or is greater than the distance from the bounding object at the front. In case 3, a small parking space is typically present in which a desired final distance of, by way of example, 0.8 m from the bounding object at the front cannot be achieved without the ego vehicle reaching its final parking position very close to the bounding object at the rear; in this case, the vehicle is oriented substantially centrally in the parallel parking space in the longitudinal direction.
A second aspect of the invention relates to a parking assistance system for performing an automated parking process for a motor vehicle in a parallel parking space. The parking assistance system includes transverse guidance device for automatically controlling the transverse movement of the vehicle and a longitudinal guidance device for automatically controlling the longitudinal movement of the vehicle. The transverse guidance device and longitudinal guidance device may be located in different controllers that communicate with one another via a vehicle bus; they may also be integrated in one controller, however. The parking assistance system is set up to move the vehicle in one or more moves into a position in the parallel parking space in which the vehicle is oriented substantially parallel to a lateral boundary line of the parallel parking space in the longitudinal direction and is at an admissible distance from the lateral boundary line of the parallel parking space. In addition, the parking assistance system is set up to determine the distance from a bounding object at the front of the parking space in this oriented position and, on the basis of the distance, to have the vehicle perform an additional corrective move in which the vehicle moves in the forward direction or the reverse direction under automatic control with a steering angle of substantially zero degrees.
The above explanations regarding the method according to the invention based on the first aspect of the invention also apply in corresponding fashion to the parking assistance system according to the invention based on the second aspect of the invention. Advantageous exemplary embodiments of the parking assistance system according to the invention that have not been explicitly described at this juncture correspond to the advantageous exemplary embodiments of the method according to the invention that are described.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.